For material removal, lasers having ultrashort laser pulses (USP) are used. Lasers are particularly denoted as ultrashort pulse lasers which emit pulsed laser light having pulse widths in the range of picoseconds and femtoseconds or shorter, having pulse durations of at most 100 picoseconds, which may be more than 10 picoseconds. Such ultrashort pulse lasers enable, in particular, a virtually melt-free and burr-free removal of the material, as long as the pulse energy is not too high. The geometries to be removed, in this instance, are usually specified in the related art by a freely programmable scanner system. In this case, the geometry is scanned on the workpiece, using a laser beam having a small beam diameter, and is removed by it piece by piece and layer by layer.
In practice, however, the removal of complex and particularly three-dimensional geometries in many cases requires unprofitably long processing times. Shortening the processing time is usually only possible by increasing the removal rates. This increase in the removal rates mostly requires an increase in the average laser power Pav=Ep·fp, where Pav is the average laser power, Ep is the pulse energy of a single pulse, and fp is the pulse frequency. If this power increase is implemented, for the same optical imaging system, only via an increase in the pulse energy Ep, the advantage of the virtually melt-free and virtually burr-free removal is usually lost.
In order to maintain the processing precision at an increased removal rate, in practice it is therefore required, as a rule, at constant pulse energy, to raise the repetition rate or pulse frequency fp. At the same time, however, to obtain the virtually melt-free removal, the overlap of the individual pulses on the workpiece has to be kept essentially constant. As a result, in practice, the feed rate of the laser beam on the workpiece mostly has to be increased in proportion to the repetition rate.
The usual scanners are, however, mostly dependent on a focusing optical system, and particularly its focal length, limited, as a rule, by the dynamics of the scanner mirror in their translational speed. In order to be able to use rapid beam sources having a high repetition rate to increase the volume removal, many beam deviation systems available in the market, such as so-called Galvo or Galvano scanners are consequently too slow. Methods and devices would therefore be desirable for processing a workpiece using laser radiation, which, on the one hand, have a high removal rate and, on the other hand, enable a high processing precision.